Thermal burns

Intro

• 70% male
• Highest incidence 18-35yo
• 77% fire or scalding
  • 43% of scalding injuries are in children <5yo
• Overall mortality rate 4%
• Risk of death increases with:
  • Burn area
  • Older age
  • Presence of inhalational injury
  • Female sex

Physiological effects of thermal injury

• Disruption of sodium pump
• Intracellular influx of sodium and water leading to cellular oedema
• Extracellular efflux of potassium
• Depression of myocardial contractility (>60% BSA)
  • Possibly due to circulating myocardial depressants
• Increased SVR i.e. not distributive shock
• Metabolic acidosis
• Increased Hct and blood viscosity
• Secondary anaemia from erythrocyte extravasation and destruction
  • Aggressive transfusion worsens morbidity and mortality however
• Local tissue injury
• Release of histamines, kinins, serotonins, arachidonic acids and free radicals
  • Cause progression of burn wound locally

Prognostic factors

• Severity of burn
• Inhalational injury
• Associated injuries
• Patients age
• Comorbid conditions
• Acute organ system failure

Pathophysiology

• Cell damage at any temperature >45 due to denaturation of cellular proteins
• Size and depth of burn depend upon:
  • Temperature of agent
  • The burning agent
  • Duration of exposure
• Zones
  • Zone of coagulation: Irreversibly destroyed with thrombosis of blood vessels
  • Zone of stasis: Stagnant microcirculation (resuscitation aims to preserve this)
  • Zone of hyperaemia: Increased blood flow

Burn size – rule of 9’s

Burn size – Lund Browder

Burn size – Hand 1%

• Area of back of patients hand = 1% BSA
• Lund-Browder is most accurate and allows accurate age-adjusted calculation
• Do not include superficial burns in calculation

Burn depth

Major burn (ACEP)

• Partial thickness >25% BSA, age 10-50
• Partial thickness >20% BSA, age <10 or >50
• Full thickness >10% BSA
• Burns of hands, face, feet or perineum
• Burns crossing major joints
• Circumferential burns of extremity
• Inhalational injury
• Electrical burns
• Burns complicated by fracture or other trauma
• Burns in high-risk patients (comorbidities/social)

Moderate burn (ACEP)

• Partial thickness 15-25% BSA in 10-50yo
• Partial thickness 10-20% BSA in <10 or >50
• Full thickness burn <10% BSA
• No major burn characteristics present

Minor burn (ACEP)

• Partial thickness <15% BSA age 10-50
• Partial thickness <10% BSA <10 or >50yo
• Full thickness <2% in anyone
• No major burn characteristics present
• Can be managed as outpatients

Inhalational injury

• Primary cause of mortality in burn injured patients
• Most fire-related deaths are due to inhalational injury
• Associated with:
  • Closed-space fires
  • Conditions that decrease mentation (intoxication, drug abuse and head injury)
• Involves heat, particulate matter and toxic gases
• Results in endothelial damage, mucosal oedema, reduced surfactant activity, atelectasis, bronchospasm and airflow obstruction

Inhalational injury

• Upper airway oedema can occur very rapidly (intubate early)
• Lower airway oedema may take 24 hours to develop
• Direct thermal injury to lower airways only occurs in steam inhalation
• Particulate matter
  • <0.5micrometres in size due to incomplete combustion of organic material
  • May reach terminal bronchioles causing inflammatory reaction, bronchospasm and oedema

Inhalational injury

• 50% of intubated burns patients suffer ARDS therefore careful fluid resuscitation is key to prevention
• Physical signs
  • Carbonaceous sputum
  • Hair loss around mouth/nose
  • Coughing
  • Facial burns
  • Hoarse voice
  • Soot in mouth or nose
  • Expiratory wheeze
  • CXR may be normal initially

Inhalational injury

• Indications for intubation
  • Full thickness burns to face or perioral region
  • Circumferential neck burns
  • Acute respiratory distress
  • Progressive hoarseness or dyspnoea
  • Respiratory depression
  • Reduced LOC
  • Supraglottic oedema and inflammation on bronchoscopy
  • Anticipated clinical course
  • High pain relief requirements

Carbon monoxide and cyanide

• CO
  • 100% O2 and consider hyperbaric oxygen therapy
  • Suspect in all and test for carboxyhaemoglobin levels
  • Remember SpO2 will be falsely elevated
• Hydrogen cyanide
  • Formed from combustion of nitrogen-containing polymers such as wool, silk, polyurethane and vinyl
  • Binds to and uncouples mitochondrial oxidative phosphorylation leading to profound tissue hypoxia
  • May require specific antidote (e.g. hydroxycobalamin)
  • May Spo2 100% but will have signs of tissue hypoxia e.g. elevated lactate

Prehospital care

• Usual primary survey
• Secondary survey with removal of all burning clothing
• Remove rings, watches, jewellery and belts as retain heat and can tourniquet
• O2 via facemask
• Careful airway attention as rapid deterioration can occur even without overt signs of airway involvement
• Consider prophylactic intubation if perioral burns in enclosed space
• IV isotonic crystalloid
• Analgesia

Initial assessment in ED

• Handover
  • Burning agent, chemical involved, duration of exposure and open/closed space
  • Assess for LOC, risk of blast injury, contact with electricity or other trauma
  • Assess adequacy of and requirement for cervical spine immobilisation
• Usual primary survey
  • For airway assess for signs of inhalational injury
  • If any evidence of airway compromise with neck swelling, burns inside mouth, or wheezing/stridor, intubate immediately
  • IV access through unburned skin if possible

Initial assessment in ED

• Secondary survey
  • Including for corneal burns
  • If partial thickness >20% BSA, NG tube insertion is routinely required due to development of ileus
  • Urinary catheter for monitoring and to prevent urinary retention in perineal burns
  • Analgesia
  • Tetanus prophylaxis

Initial assessment in ED

• Bronchoscopy for suspected inhalational injury in intubated patients for both diagnostic and therapeutic purposes
• Treat suspected inhalational injury
  • 100% O2
  • Intubation and ventilation
  • Bronchodilators
  • Aggressive pulmonary toilet
  • Consider hyperbaric O2 for severe CO poisoning

Pregnant patients

• High risk of spontaneous miscarriage in large BSA burns
• Resuscitation requirements may exceed that of guidelines (remember blood volume increased 50%
• Outcome depends on severity of mothers burn and subsequent resuscitation

Fluid resuscitation

• Should be guided by cardiorespiratory status and urine output
• Start with modified Parkland and adjust according to response
  • For adult BSA >20% deep-partial and full thickness and children >10% (as per VicBurns)
• Adults
  • 2mL/kg/BSA % over 24 hours of Hartmann’s
  • Half in first 8 hours and rest over 16 hours
  • 4mL/kg/BSA for electrical burns
• Children
  • 3mL/kg/BSA% + Maintenance over 24 hours of Hartmann’s
  • Half in first 8 hours and rest over 16 hours
• Aim for UO 0.5mL/kg (1mL/kg in children who are haemodynamically normal)
• Will need more if concomitant multisystem trauma or inhalational injury
• Need very close monitoring, especially if comorbid cardiorespiratory or renal disease

Rhabdomyolysis

• Electrical injuries, incineration burns and associated crush injuries may produce rhabdo and myoglobinuria with risk of renal failure
• Therapy to limit renal damage from this is crucial

Wound care

• Cover with clean, dry sheet or clingfilm
• Later can cover with saline-soaked dressings
• Cooling stablilises mast cells and reduces histamine release, kinin formation and thromboxane A2 production
• For large burns, saline-soaked dressings may result in hypothermia so sterile drapes are preferred

Escharotomy

• Circumferential burns may compromise distal circulation, particularly after resuscitation initiated
• If vascular compromise is evident, escharotomy is indicated
• Scalpel to depth of fat on mid-lateral portion of limbs
• Can extend to hands and fingers
• Anterior axillary line from 2^nd rib to 12^th rib joined tranversely across chest wall for chest wall escharotomy

Pain control

• Local cooling is soothing but does not provide pain control
• IV route preferred initially
• Anxiolytics may also assist control of situation
• Ketamine infusions are sometimes required

Minor burn care

• First aid 20 minutes of cool running water
• Even if <10% BSA, those over joints, in special areas (axillae, groin, face, hands, feet), extremes of age, comorbidities, challenging social situations or inadequate pain control will still require inpatient care
• After analgesia, clean the wound with dilute antiseptic solution or saline
• Debride ruptured blisters
• Debride large intact blisters or those over very mobile joints
• Small blisters on immobile areas should be left intact
• Tetanus prophylaxis

Minor burn care

• Dressing choice
  • If deep partial thickness, full thickness or contaminated:
    • Silver or antimicrobial dressings
  • If superficial and not contaminated:
    • Standard dressings

Minor burn care

• Standard dressings
  • Absorbant
    • Foams: Allevyn, Mepilex, Mepilex border, mepilex XT
    • Alginates: AlginateM, Melgisorb Ag, Kaltostat
    • Other: Aquacel, paraffin gauze with adequate secondary dressing
  • Balance
    • Silicone: Mepitel, Mepitel One, Mepilex Transfer
    • Non-stick: Jelonet
    • Hydrocolloids: Duoderm
  • Hydrate
    • Cream gels: Solusite with secondary dressing
    • Burn Aid or water Jel

Minor burn care

• Antimicrobial dressings
  • Absorb
    • Acticoat 3 or 7 (3 if want pt to be seen earlier as not trustworthy)
    • Aquacel Ag
    • Mepilex Ag/Mepilex BorderAg
    • Melgisorb Ag
    • Allevyn Ag
  • Balance
    • Acticoat 3 or 7
    • Mepilex Transfer Ag
  • Hydrate
    • Flamazine (1% silver sulfadiazine)
    • SSD (silver sulfadiazine)

Who needs referral to burns centre?

• Suspected inhalational injury
• Suspected cellulitis/infection
• >10% TBSA
• Full thickness >5% TBSA
• Special areas: Hands, feet, genitals, face, perineum and major joints
• Electrical burns
• Chemical burns with associated inhalational injury
• Circumferential burns
• Children or elderly
• Significant comorbidities e.g. T2DM, immunosuppression
• Pregnant
• Associated trauma

Last Updated on October 9, 2020 by Andrew Crofton